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Discovered in 1929 by Phoebus Levene, [4] deoxyribose is most notable for its presence in DNA. Since the pentose sugars arabinose and ribose only differ by the stereochemistry at C2′, 2-deoxyribose and 2-deoxyarabinose are equivalent, although the latter term is rarely used because ribose, not arabinose, is the precursor to deoxyribose.
In other forms of life many other sugars are used and various donors are utilized for them. All five of the common nucleosides are used as a base for a nucleotide sugar donor somewhere in nature. As examples, CDP-glucose and TDP-glucose give rise to various other forms of CDP and TDP-sugar donor nucleotides. [9] [10]
This nucleotide contains the five-carbon sugar deoxyribose (at center), a nucleobase called adenine (upper right), and one phosphate group (left). The deoxyribose sugar joined only to the nitrogenous base forms a Deoxyribonucleoside called deoxyadenosine, whereas the whole structure along with the phosphate group is a nucleotide, a constituent of DNA with the name deoxyadenosine monophosphate.
They are the molecular precursors of both DNA and RNA, which are chains of nucleotides made through the processes of DNA replication and transcription. [2] Nucleoside triphosphates also serve as a source of energy for cellular reactions [3] and are involved in signalling pathways. [4]
The code is read by copying stretches of DNA into the related nucleic acid RNA in a process called transcription. Within cells, DNA is organized into long sequences called chromosomes. During cell division these chromosomes are duplicated in the process of DNA replication, providing each cell its own complete set of chromosomes.
DNA is a long polymer made from repeating units called nucleotides. [ 6 ] [ 7 ] The structure of DNA is dynamic along its length, being capable of coiling into tight loops and other shapes. [ 8 ] In all species it is composed of two helical chains, bound to each other by hydrogen bonds .
From glycolysis, glucose 6-phosphate is a precursor for histidine; 3-phosphoglycerate is a precursor for glycine and cysteine; phosphoenol pyruvate, combined with the 3-phosphoglycerate-derivative erythrose 4-phosphate, forms tryptophan, phenylalanine, and tyrosine; and pyruvate is a precursor for alanine, valine, leucine, and isoleucine.
Nucleosides are glycosylamines that can be thought of as nucleotides without a phosphate group.A nucleoside consists simply of a nucleobase (also termed a nitrogenous base) and a five-carbon sugar (ribose or 2'-deoxyribose) whereas a nucleotide is composed of a nucleobase, a five-carbon sugar, and one or more phosphate groups.